1. Field of the Invention
The present invention relates to a method of conducting well operations from a moveable floating platform floating on a body of water.
2. Description of the Prior Art
As the exploration for oil and gas reserves has extended into deeper offshore waters new technology has been developed that makes possible the drilling and production of offshore wells. Bottom-supported platforms have been typically used to drill and produce these wells in water depths now reaching up to 1500 feet. Due to the high cost of these bottom-supported structures, however, floating platforms are typically used in deeper water. As can be imagined, however, the large capital expenditures associated with the fabrication and installation of any type of platform in these deep water depths dictates that any discovered field of petroleum reserves be economically developed as soon as possible.
In the typical development of an offshore field of petroleum reservoir(s) all of the wells are drilled, thereafter all of the wells are subsequently completed and production is then started from the field. But this sequence of operations may result in one or more years delay before any oil and/or gas production from the field is sold. Only after production is sold can any amount of return on the investment required for the offshore platform be realized.
As can be imagined, methods have been studied that accelerate the positive cash flow from a field in order to offset the carrying costs of the initial capital outlay required for the fabrication and installation costs of the platform (and drilling costs). To quickly retire the debt associated with the large capital expenditure, wells may be placed on production while new wells are being drilled. In this method a first well is drilled, completed and placed on production almost simultaneously with the start of the drilling of the second well. In this manner early oil and/or gas production from the field may be used to quickly pay off the initial fabrication, installation and drilling costs. This "drilling while producing" operation has been typically practiced from bottom-supported and tension leg platforms.
A problem exists, however, in drilling a plurality of wells from a bottom-supported structure or a tension leg platform structure because the location of each well upon the bottom of the body of water is fixed by the location of well conductors in the case of the bottom-supported platform or by the location of the template used to anchor the tension leg platform. But as each new well is drilled, and it's geological structure studied by use of "logging" and/or other tools the ideal bottom location of each additional well can be readily determined. For example, after a few wells are drilled it may be found that the next series of wells should be drilled approximately 300 feet from the existing position of the platform. But, due to the immobility of the template beneath the floating platform or the conductors of the bottom-supported platform the wells drilled from bottom-supported or tension leg platforms may only be initiated in a set location not favorable to more economic field development.
A method need be developed therefore that allows the location of additional wells to be adjustable on the bottom of the body of water as the field development progresses. This method should allow the most favorable placement of the drainage pattern while development of the field progresses.